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↣ How long can I leave beer in the primary?


What is the risk of leaving a beer in the primary fermenter too long?


One can leave the beer in the primary fermenter as long as one needs. There is no maximum time limit, though there a couple of risks to keep in mind.

Many brewers simply follow the beer recipe or instructions on the malt kit and leave their wort to ferment for around a week to ten days. This usually allows enough time for fermentation to have completed.

And technically that's OK, it's time to bottle.

But the mystery and muscle of brewing beer are that there is a whole range of chemical processes happening in that primary wort. Sure the yeast may have produced enough alcohol to make a good drop of beer but there are still a few things that happen.

The longer you leave your beer, the more chance the yeast has to get rid of smells and other leftovers from the fermentation process.

A great example of this is the presence of acetaldehyde in the wort.This chemicals forms at the beginning of the fermentation process. It tastes like sour green apple and is not really conducive to a good brew.

What's the best way to get rid of this apple taste? 

Let the yeast take the time to convert it to ethanol (alcohol).

So leaving your beer for longer than the recommended instructions on the tin of the beer kit is pretty much a smart move. Frankly given the benefit to the beer and thus the kit manufacturer's reputation, I do not know why they don't frame the time as a minimum.

That said, when I followed Te Aro's brewing instructions for their Obligatory ale, I made damn good beer.

Exceptions aside, the longer you condition your beer, the greater reduction in acetaldehyde that will occur and the beer your beer will take.

Stout beers have even more to work through so they can happily take longer in the primary.

Another benefit of leaving the beer in the primary for longer is that there is a greater chance that your beer will clear more sediment, thus giving you clear beer

Many a brewer likes to see their lager look like a lager - that classic light yellow / orange combo. Sure, some wheat beers can be a bit hazy. And the end of the day this comes down to personal preference as the beer taste is not generally affected.

What about extra long times?

Many brewers have reported leaving batches for months and suffered no issues. I'd reason though that the beer was stored in a cool place - a beer wort left in a hot environment is sure to fail as the yeast would probably get cooked. 

There is an issue that can happen called autolysis. 

This is when the yeast cells die, giving off some potentially off flavours. These could be hydrolytic enzymes, lipids, and metal cations that can contribute to off flavour. If you've made a healthy batch with a quality yeast, pitched at a good temperature and brewed in a stable environment, then the risks of autolysis are quite low. 

If you are quite concerned about this, you could counter by racking your beer to a secondary, thus removing the yeast cake from the equation.

It's important to note, the same process begins again when the beer is bottle conditioned - more sugar is added to the beer for the yeast to eat - this is because CO2 is the by-product of fermentation and is trapped in the beer. Most beers strongly benefit from being bottle conditioned for three weeks before consumption.

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